Direct fuel injected engines

ABSTRACT

In a two-stroke spark ignition engine, fuel is injected through the cylinder wall at a location opposite to and above the level of the exhaust port (120). The fuel is delivered in the form of a number of streams such as, for example, streams (60), (61), (62). One of the streams (60) is directed upwardly across the cylinder to deliver fuel towards the combustion chamber cavity (122). This stream (60) is arranged not to impinge on the spark plug (123) but is caused to create a fuel rich cloud within the cavity (122). Streams (62) are directed downwardly and outwardly from the injection location and an optional stream (61) may be directed across the cylinder towards the exhaust port side of the cylinder.

This application relates to delivering fuel to an engine by injectingthe fuel directly into the combustion chamber.

In order to maintain the exhaust emissions of an engine within theprescribed limit it is desirable to effectively distribute the fuelwithin the combustion chamber. One mode of reducing exhaust emissions isto ensure that the fuel is exposed to sufficient air to burn the fueland so avoid release of unburnt hydrocarbons in the exhaust.

This problem is more pronounced in engines operating on the two strokecycle because of the late timing of the closure of the exhaust port inthe compression stroke. If the fuel is delivered a significant timebefore final closing of the exhaust port, some fresh fuel may escape tothe exhaust, particularly at low engine speeds. However if injection isdelayed until after the exhaust port is fully closed, there is limitedtime available to effect delivery and obtain effective dispersion of thefuel within the combustion chamber before ignition. This is ofimportance at high fuelling rates, and particularly at high engine speedwhich creates a further restraint.

Characteristics of the spray of the fuel droplets issuing from a nozzleinto a combustion chamber also have a major effect on the efficiency ofthe burning of the fuel, which in turn affects the stability of theoperation of the engine, the fuel efficiency and the exhaust emissions.

In order to optimise these features in a spark ignited engine thedesirable characteristics of the spray pattern of the fuel issuing froma nozzle include small fuel droplet size, controlled penetration of thefuel spray into the combustion chamber and, at least at low engineloads, a relatively rich mixture in the vicinity of the spark plug. Morespecifically in the control of the harmful components of the engineexhaust, it is desirable to control the placement of the fuel within thegas charge in the combustion chamber to meet a number of differentparameters. Ideally the fuel should be distributed in the gas charge sothat the resultant fuel-air mixture is readily ignitable at the sparkplug, all the fuel has access to sufficient air to burn completely, andthe flame is at a sufficient temperature to extend to all the fuelbefore being extinguished. There are other factors that must also beconsidered, such as combustion temperatures that may promote detonation,or the formation of undesirable contaminants in the exhaust gas.

It is therefore the principle object of the present invention to providea method and apparatus for delivering fuel to an internal combustionengine that will assist in achieving the required level of fuel economyand exhaust emissions.

With this object in view there is provided a method of feulling a twostroke cycle spark ignited engine having a cylinder in which acombustable charge is prepared, and a cylinder head closing one end ofsaid cylinder and having a cavity therein communicating with thecylinder, an ignition means to ignite the combustable charge in saidcavity, a piston supported to reciprocate in said cylinder, and anexhaust port in said cylinder spaced from said cylinder head, saidmethod comprising injecting a metered quantity of fuel into the cylinderat a location between the level of the exhaust port and the cylinderhead and in a manner to direct part of the fuel in a direction to enterthe cavity in the cylinder head and to direct another part of the fuelinto that part of the cylinder on the opposite side of a diametral planeof the cylinder at the location of injection of the fuel to thecylinder.

Conveniently the fuel is divided into a number of streams extending intothe cylinder, one said stream delivering fuel towards the cylinder head,to enter the cavity and at least one said stream being directeddownwardly and across the cylinder.

The injection of the fuel may be effected through the side wall of thecylinder through an injector nozzle at a location which will result inthe nozzle being covered by the piston during a portion of the enginecycle.

The nozzle may be of a form which will deliver the fuel into thecylinder as a curtain of generally conical form which may be unbroken ordivided into a number of segments. Alternatively the nozzle may have aplurality of orifices with an individual stream of fuel issuing fromeach orifice. In this latter form each stream is preferably in a conicalform. The conical curtain of fuel in the continuous or broken form orthe plurality of streams, are preferably all based on a fueldistribution of conical form having an included angle of 120°±30°.

A conventional two stroke cycle engine normally has two or more transferports spaced circumferentially in the cylinder wall and through whichair is admitted to the cylinder. The injection of the fuel may beeffected at a location directly above the transfer port if there is onlyone, or in a multi-transfer port cylinder, directly above the principaltransfer port, which is usually located centrally with respect to theother transfer ports in the circumferential direction.

Preferably a plurality of streams of fuel are directed across thecylinder, and diverging with respect to the axial plane of the cylindercontaining the upwardly directed stream. In a multi-transfer portcylinder the diverging streams are arranged to feed fuel into the airentering the cylinder through the respective side transfer ports. Thediverging streams may be also downwardly directed with respect to thediametral plane of the cylinder at the level of the injector.

The directing of fuel to enter the cavity in the head establishes arelatively rich fuel-air mixture in the vicinity of the spark plug toensure ready ignition of the cylinder charge. The fuel directed acrossthe cylinder exposes that part of the fuel to the fresh air chargeentering the cylinder from the transfer ports and hence to the maximumquantity of air so to aid the effective mixing thereof for completecombustion of the fuel.

Also the downward directing of some of the fuel exposes it to the hightemperature top surface of the piston to reduce the quenching effect ofthe incoming fuel on the air charge.

The directing of the fuel into the various streams may be achieved byproviding respective orifices in a nozzle, each orientated in therespective direction to provide fuel streams in the required streamdirections. The size of the respective orifices may be selected so thatthe quantity of fuel in each stream may differ to also contribute toachieving the required fuel distribution within the combustion chamber.

The fuel may be injected as fuel alone, but is preferably entrained in agas such as air or other combustion supporting gas. The entraining ofthe fuel in a gas assists in atomising the fuel as it is deliveredthrough the injection nozzle.

The degree of penetration of the fuel streams into the combustionchamber may be controlled by regulating the pressure of the fuelsupplied to the nozzle. An increase in the fuel supply pressure may beused to increase the extent of penetration of the fuel from the nozzleinto the combustion chamber. The change in the pressure of the fuelsupply may be in response to a change in engine speed. Conveniently, thepressure of the fuel supply is increased by a set amount upon the enginereaching a selected engine speed.

In one arrangement the distribution pattern of fuel from the injectionnozzle is similar for all fueling rates. In other embodiments, thedistribution pattern of fuel is varied substantially, in accordance withdiffering engine speed and load conditions.

When injection is effected through the cylinder wall as currentlyproposed rather than through the cylinder head as is conventional, itwill be appreciated that the injection must be completed before theinjector nozzle is covered as the piston rises in the cylinder duringthe compression stroke.

It is therefore preferred that the injector nozzle be located above thelevel of the upper edge of the exhaust port, this edge determining thtiming of the exhaust port closure in the engine cycle. It is to benoted that normally in a two stroke engine the transfer ports arepositioned to close about the same time, and preferably not later, inthe engine cycle than the exhaust port closure.

Also it has been found desirable to vary the timing of the injectionperiod in relation to exhaust port closure.

As previously referred to, many two stroke cycle engines have two ormore transfer ports spaced circumferentially in the cylinder wall, andthis arrangement assists in obtaining distribution of the fresh chargein the cylinder, and in scavenging of the exhaust gases from all areasof the cylinder. The transfer port arrangement may vary from a singleport, generally diametrically opposite the exhaust port, to a pluralityof ports, generally located in the 180° of arc of the cylinder wallopposite the exhaust port. In order to promote scavenging, the transferports are shaped to provide in the incoming air a velocity component inthe direction towards the cylinder head.

Thus if the injection nozzle is located in the cylinder head, theincoming air and the injected fuel are moving in generally oppositedirections. The distribution of the fuel in the cylinder is thusinhibited, and in particular the flow of fuel towards the transfer portsis inhibited due to the contra-flow of the incoming air so a low fueldensity will exist immediately adjacent the transfer ports. Naturallythe area of the cylinder adjacent the transfer ports is an oxidant richarea, and thus if not adequately fuelled this oxidant is not fullyutilised.

Having regard to the above referred to considerations, the preferredlocation of the injection of the fuel is in the cylinder wall above thetransfer port or ports, and between the level of the exhaust port andthe cylinder head. This results in a major part of the delivered fuelbeing directed into the path or paths of the air entering the cylinderthrough the transfer ports.

With this arrangement of the fuel and air entering from the same side ofthe cylinder, at high engine speed operation the fuel is effectivelytransferred across the chamber in the short time available, while alsoachieving distribution of the mixture throughout the combustion space inthe cylinder. This arrangement thus tends to result in a homogeneouscharge in the combustion space, which is desirable for high speed andload performance.

In addition, the stream of fuel directed into the cylinder head cavityprovides the advantage of a somewhat stratified fuel charge in the areaof combustion initiation, which provides improved part load engineperformance without substantial detrimental effects on the highspeed/load performance.

Testing has shown that the spray pattern from the injector nozzle shouldbe such that between approximately 30 and 60 percent of the mass of fuelinjected should be directed above the diametral plane of the cylinderthat passes through the axis of the injector nozzle, the balance beingdirected below said plane. The actual distribution of the fuel will varywith different engines and the operational requirements. A balance isselected on the basis that at low fueling rates a high proportion of thefuel should be directed upwardly and at high fueling rates a highproportion should be directed downwardly. In engines which operatemainly in the high load range, such as outboard marine engines, thedistribution is preferably one third of the fuel upwardly toward thecylinder and two thirds downwardly. More generally between 33 to 50percent of the fuel should be delivered above said diametral plane. Thefuel may issue from the nozzle in the form of three streams angularlyspaced equally about the axis of the nozzle with only one streamdirected above the nozzle axis. Each stream may issue in a generallyconical form which may have an included angle of about 30°.

It will be appreciated that different distributions of the fuel may beobtained with different angular relationships between the respectivestreams, and the different cone angle of the stream. Normally however,one stream is directed above the axis of the nozzle and the other twostreams are directed below the axis at an angular spacing to provide therequired proportion of fuel above and below the cylinder's diametralplane through the nozzle axis. The angular spacing between the twodownwardly directed sprays at the nozzle may conveniently vary between90° and 150°.

One embodiment of the nozzle also includes a further stream issuingaxially from the nozzle and of a size so approximately 5 percent of thetotal fuel quantity issues therefrom.

The above discussed disribution into three fuel streams is convenientlyachieved by providing a valve regulated orifice to control the timing ofthe fuel delivery in the engine cycle and the duration of delivery, anda nozzle plate downstream of the orifice. The nozzle plate has a seriesof apertures therein to divide the fuel mass into three streams directedas above described. Alternatively it is possible to control the fuelflow by particular configurations of a poppet valve, and both theseconstructions will be described in further detail later in thisspecification.

In these constructions there may be varying degrees of wall attachmenteffects as the fuel issues into the cylinder. The wall attachment effectis the characteristic of a fluid flowing over a surface to tend tofollow the contour of that surface rather than separate therefrom atrelatively abrupt changes in the direction of the surface.

Advantage of the wall attachment effect at the injector nozzle can betaken to direct part of the fuel flowing through the nozzle to flowalong the surface surrounding the nozzle orifice or orifices. In aconstruction where the injector nozzle is located in the wall of anengine cylinder, use may be made of the wall attachment effect to causesome of the fuel delivered through the nozzle to flow in a directionalong or generally parallel to the cylinder wall, generally in adirection normal to the nozzle axis. This flow has been shown to beparticularly advantageous in mixture preparation in the engine whenoperating in high speed/load conditions, as it is desirable under suchconditions to deliver fuel to the incoming air charge close to thetransfer ports.

In order to further describe the fuel spray distribution reference willbe made to the accompanying drawings illustrating particular practicalarrangements of the injector nozzle and resulting spray patterns.

In the drawings:

FIG. 1 is sectional view of a single cylinder and piston of a two strokecycle reciprocating engine employing crankcase compression to charge thecylinder.

FIG. 2 is a diametral section of the engine in FIG. 1 along the plane2--2.

FIG. 3 is a diagrammatic representation of a fuel spray pattern viewedin the direction of the injection nozzle axis.

FIG. 4 is a diagram similar to FIG. 3 of the fuel spray viewed indirection A shown in FIG. 3.

FIGS. 5 and 6 are polar diagrams of the fuel mass flux in the cylinderresolved into the directions corresponding to FIGS. 3 and 4respectively.

FIG. 7 is a side view partly in section of a fuel metering and injectionunit, suitable for use with the engine shown in FIGS. 1 and 2, andshowing diagrammatically attached ancillary equipment.

FIG. 8 is a diagrammatic part-sectional view of the combustion chamberarea of an engine similar to that of FIGS. 1 and 2 and incorporating thenozzle shown in FIGS. 9 and 10.

FIGS. 9 and 10 show a further form of nozzle which may be used to obtainthe desired fuel distribution in the combustion chamber.

FIG. 11 is a view partly in section of a poppet type valve andco-operating seat suitable as an injector nozzle for use in the injectorunit shown in FIG. 7.

FIG. 12 is a cross-sectional view through the head of the valve in FIG.11.

Referring now to FIGS. 1 and 2, the engine overall is of generallyconventional construction. The combustion chamber 125 is defined bycylinder 110, cylinder head 121 and piston 112 is coupled by theconnecting rod 113 to the crankshaft 114 in crankcase 111. The crankcaseincorporates air induction ports 115 provided with conventional reedvalves 119, and three transfer passages 116 that communicate thecrankcase 111 with respective transfer ports, a central transfer port118 and two flanking transfer ports 117 and 119.

The transfer ports are each formed in the wall of the cylinder 110normally with their respective upper edge located in the same diametralplane of the cylinder. An exhaust port 120 is formed in the wall of thecylinder generally opposite the central transfer port 118. The upperedge of the exhaust port may be slightly above the diametral plane ofthe transfer ports' upper edges, as shown in FIG. 1.

The cylinder head 121 has a central combustion cavity 122 into which thespark plug 123 extends. The fuel injector nozzle 124 is located in thecylinder wall directly above the central transfer port 118. The nozzle124 is in this example located above the upper edge of the transfer portsuch that its axis is between half and three-quarters of the distancefrom said edge to the top of the cylinder. Generally the nozzle islocated so that it is not completely covered by the piston until thepiston is in a position corresponding to a crankshaft position between60° and 70° before the top dead centre position of the piston. It willbe appreciated that the nozzle will be uncovered at a correspondingposition of the piston and crankshaft after top dead centre. Also therewill be a period during which the nozzle progressively covered anduncovered by the piston. Typically, this period may be equivalent toapproximately 10° of rotation of the crankshaft.

It has been found that the timing of injection of the fuel injectionrelative to the closure of the exhaust port 120 is a relevant factor inobtaining the required degree of mixing of the fuel with the incomingair, and avoiding undue loss of fuel through the exhaust port. Effectivemixing of the fuel with the air and limiting of fuel lost through theexhaust port improves fuel economy and reduces hydrocarbon emissions.

In this regard, it is desirable to control the injection timing so thatthe mid-point of the injection period is substantially a uniform timeinterval before exhaust port closing. It is believed that thedesirability of this time interval is related to the velocity of theincoming air charge and the diameter of the cylinder, the latterrelating to the distance from the transfer port to the exhaust port.Tests on a two cylinder outboard marine engine having cylinder bores of80 mm, have indicated that the time interval from injection mid-point toexhaust port closure should be approximately 3 ms over the normaloperating speed range of 2,000 to 5,000 R.P.M. At the lower end of thespeed range, this is desirably decreased, as for example toapproximately 2 ms at 1,000 R.P.M.

Typical injection timings for the engine used in the above referred totests, having exhaust port closure at 262.5° after top dead centre, areas following: (All timings are in degrees after top dead centre).

    ______________________________________                                        Engine Speed          Injection                                               R.P.M.     Start      Finish   Mid Point                                      ______________________________________                                        1,200      245        274        259.5                                        2,000      214        258      236                                            3,000      232        298      265                                            4,000      192        266      229                                            5,000      114        224      169                                            5,500       95        207      151                                            ______________________________________                                    

Referring now to FIGS. 3 and 4 there is shown a typical distribution ofthe fuel sprays about the axis of the nozzle and in respect to thecylinder wall respectively. The nozzle 124 is arranged to give threemain streams of fuel the centrelines of which are designated 30,31 and32. The stream 31 is directed upwardly to deliver fuel into the cylinderhead cavity 122 and consequently the direction of said stream isprincipally determined by the relative positions of the cavity 122 andthe spark plug 123 to the injection nozzle 124. The cavity 122 has itscentral plane coincident with the axial plane of the cylinder passingthrough the centre of the exhaust port 120 and the central transfer port118. The axis of the nozzle 124 is also located in the aforesaid plane.the two downwardly directed streams 30 and 32 are symetrical withrespect to the above referred to axial plane and the centreline or axisof each spray is preferably located within a cone having an includedangle between 90° and 150° and extending from the tip of the nozzle. Thecone need not be coaxial with the axis of the nozzle, and may beinclined thereto in said axial plane. The angles B and γ shown in FIG. 4may each vary from 15° to 60° the choice of such angles being dependentupon the particular engine fuelled. The angles referred to above are asprojected onto the planes as represented in the drawings.

FIGS. 5 and 6 are polar diagrams of the fuel mass distribution in thecylinder with the three fuel streams arranged as shown in FIGS. 3 and 4.The polar diagrams represent the fuel distribution resolved into the twoplanes which are represented by FIGS. 3 and 4. The length of the vectorfrom the centre of the nozzle to the plot in any direction representsthe fuel density in the cylinder in that direction.

The injector nozzle 124 indicated in FIG. 1 is an integral part of afuel metering and injection system preferably of the type wherein fuelentrained in air is delivered to the combustion chamber of the engine bythe pressure of the air supply. One particular form of fuel metering andinjection unit is illustrated in FIG. 7 of the drawings.

The fuel metering and injection unit incorporates a suitably availablemetering device 130, such as an automotive type throttle body injector,coupled to an injector body 131 having a holding chamber 132 therein.Fuel is drawn from the fuel reservoir 135 delivered by the fuel pump 136via the pressure regulator 137 through fuel inlet port 133 to themetering device 130. The metering device operating in a known mannermeters an amount of fuel into the holding chamber 132 in accordance withthe engine fuel demand. Excess fuel supplied to the metering device isreturned to the fuel reservoir 135 via the fuel return port 134. Theparticular construction of the fuel metering device 130 is not criticalto the present invention and any suitable device may be used.

In operation, the holding chamber 132 is pressurised by air suppliedfrom the air source 138 via pressure regular 139 through air inlet port145 in the body 131. Injection valve 143 is actuated to permit thepressurised air to discharge the metered amount of fuel through injectornozzle 142 into a combustion chamber of the engine. Injection valve 143is of the poppet valve construction opening inwardly to the combustionchamber, that is, outwardly from the holding chamber.

The injection valve 143 is coupled, via a valve stem 144, which passesthrough the holding chamber 132, to the armature 141 of solenoid 147located within the injector body 131. The valve 143 is biased to theclosed position by the disc spring 140, and is opened by energising thesolenoid 147. Energising of the solenoid 147 is controlled in timedrelation to the engine cycle to effect delivery of the fuel from theholding chamber 132 to the engine combustion chamber.

Further details of the operation of the fuel injection systemincorporating a holding chamber is disclosed in Australian PatentApplication No. 32123/84 and corresponding U.S. patent application No.740,067 filed 2nd Apr. 1985, the disclosures of which are incorporatedherein by reference.

The energising of the solenoid 147 is timed in relation to the enginecycle by a suitable electronic processor 150. The processor receives aninput signal from the speed sensor 151 which signal is indicative of theengine speed and also identifies a reference point in the engine cyclein respective or which operations may be timed in relation to the enginecycle. The processor 150 also receives a signal from the load sensor 152which signal is indicative of the air flow rate to the engine airinduction system. The processor is programmed to determine from the airflow rate signal the load demand on the engine.

The processor 150 is further programmed to determine from the speed andload conditions of the engine the required timing of the injection ofthe fuel into the combustion chamber.

Conveniently the processor incorporates a multipoint map designating therequired injection timing for a range of engine loads and speeds, thesehaving been determined from tests carried out to obtain required enginepower and exhaust emisssion levels. The processor is similarlyprogrammed to determine from a multipoint map the required ignitiontiming of the engine in relation to engine load and speed as previouslydiscussed.

The processor provides appropriate signals to the injector actuator 153and ignition actuator 154, in accordance with the determinations, toenergise the solenoid 147 at the required time for fuel ignition, andactivate the spark plug 123 at the required time for ignition. Thegeneral construction of the load and speed sensors suitable for use asabove indicated are well known in the industry, as are processors forperforming the functions required by the processor 150.

FIG. 9 is a sectional view and FIG. 10 a front end view of a form ofnozzle plate for use in the engine cylinder wall to obtain the desiredfuel distribution in the cylinder. This nozzle is used in conjunctionwith the conventional poppet valve as shown in FIG. 7, which times andregulates a supply of fuel to the nozzle. The nozzle plate is fitted tothe end of the injector body 131 to enclose the valve 143. Fuel issupplied to the central bore 50 from the valve 43, and issues from thenozzle through the three orifices 51, 52 and 53 of equal diameter. Theorifices are equally spaced angularly about the axis of the bore 50,although, the axis of the orifice 52 is inclined at 50° to the axis ofthe bore, whereas the axes of the orifices 51 and 53 are inclined at 45°thereto. In a modified form the nozzle may include an axial orifice 54as shown in broken outline. This axial orifice is considerably smallerin diameter than orifices 51, 52 and 53 so that approximately 5 percentof the total fuel issues therefrom.

The nozzle shown in FIGS. 9 and 10, and described above as the modifiedform with orifice 54 may be used to provide a fuel distribution in anengine combustion chamber as shown in FIG. 8. The position of the nozzle124 is selected so that, with the particular patterns of fuel streamsthat are created by the arrangement of orifices in the nozzle, thestreams will not impinge strongly on the various surfaces of thecombustion chamber and create undue wetting of these surfaces with fuel.Another factor influencing the position of the nozzle 124 is thatadequate time must be provided to complete injection of the fuel beforethe piston moves to close to the lower of the streams of fuel issuingfrom the nozzle. Preferably the nozzle should be located so that thepiston will not interfere with the fuel streams prior to the last 90° ofcrank movement on the piston compression stroke.

As seen in FIG. 8, the stream 60 of fuel from the nozzle 124 is directedupward across the cylinder to deliver fuel towards the cavity 122. Thestream 60 is arranged not to impinge on the spark plug 123 as this wouldtend to create undue deposits thereon. However, the stream 60 willcreate a fuel rich cloud within the cavity 122 that will be readilyignitable by the spark plug.

The fuel stream 61 is directed across the cylinder toward the exhaustport side of the cylinder. The two fuel streams 62 diverge to eitherside of the stream 61 to provide fuel to the respective side areas ofthe cylinder. These streams 62 are also directed downwardly below thediametral plane of the stream 61 towards the crown 108 of the piston112. The streams 62 provide fuel to the air entering through the sidetransfer ports in a multi-transfer port engine, and provide fuel to theoxidant-rich transfer region as the piston moves upwardly so takingcharge toward the top of the cylinder due to turbulence effects createdby piston movement.

FIGS. 11 and 12 are views of a suitable alternative construction ofpoppet valve 143 and co-operating seat of the nozzle 142 therefor, forincorporation in the injector body 131 previously described. Thisalternative produces a spray pattern with two streams rather than thethree or four streams as described above.

The port 49 has an outwardly tapered mouth 35 having a seating surface29 which co-operates with the seating surface 32 for the valve 33.Immediately inward of the mouth 35 is the cylindrical throat 36 whichmerges at 37 with the axial fuel supply passage 38. The poppet valve 33has a conventional tapered head 39 to co-operate with the tapered mouth35 and a cylindrical stem 40. Between the head 39 and the stem 40 thereis a cylindrical boss 41 with a tapered portion 42 which merges with thestem 40.

The boss 41 and tapered portion 42 are scalloped out as indicated at 43and 44 to provide areas of increased flow path between the boss 41 andthe throat 36. The scalloped areas 43 and 44 are separated by acircumferentially narrow axial surface 45 and a circumferentially wideaxial surface 46 of the boss.

When installed in the engine cylinder wall the nozzle is positioned sothat the circumferentially wide axial surface 46 is uppermost towardsthe cylinder head 121 and the narrow axial surface 45 lowermost. As aresult of the additional restrictions of fuel flow in the areas of thenozzle where the surfaces 45 and 46 are located, this nozzle willprovide greater fuel flow into the cylinder in the downward directionthrough the scallops 43 and 44 than there is in the upward direction.Also as the scallops are outwardly oriented, the flow therethrough willbe directed laterally to either side of the cylinder.

Other configurations of valves and seats may be used to achieve therequired distribution of fuel issuing into the engine cylinder.Generally the configuration of the valve and seat is required to formrespective streams of fuel droplets directed upwardly and downwardlywith respect to the diametral plane of the cylinder at the nozzle withthe apropriate proportions of the total amount of fuel in the respectivestreams.

A fuel metering and injection method and apparatus suitable for use inthe practice of this invention is disclosed in each of pendingAustralian Patent Applications Nos. PH2876 and PH3343, and thedisclosures in each of these applications is hereby incorporated in thisspecification by reference. The specifications of these particularapplications disclose nozzles incorporating a valve and complementaryseat wherein fuel is delivered to the passage, formed therebetween whenthe valve is in the open position, through a number of peripheral spaceorifices in the seat. Nozzles in accordance with these constructions maybe used in practicing the present invention.

In this specification there has been specific reference to the directionand shape of the fuel droplet spray issuing into the engine from theinjector nozzle. It will be appreciated that these features will beinfluenced by the conditions within the engine combustion chamber intowhich the fuel is injected, including the directions and velocities ofthe movement of the gas charge in the combustion chamber. Theseconditions and other dynamic influences preclude accurate defining ofthe fuel spray shape and direction under actual operating conditions.Accordingly the features of direction and shape of the fuel dropletspray referred to herein are described as determined in still air atatmospheric pressure and in the trajectories as shown in the drawings.

Reference has been made in the specification to varying the degree ofpenetration of the fuel spray into the combustion chamber with engineload and this may be achieved by varying the pressure of the fluideffecting injection. There is described in our Australian PatentApplication No. PH1560 a method and apparatus for varying the pressureof a gas in which fuel is entrained, the fuel being injected into anengine combustion chamber by the pressure of the gas. That method andapparatus is suitable for use in conjunction with the method andapparatus of the present invention and by this reference to AustralianPatent Application No. PH1560 the disclosure therein is herebyincorporated in this specification by reference.

This invention is applicable to two stroke cycle internal combustionengines for all uses and is particularly useful in contributing to fueleconomy and the control of exhaust emissions in engines for or invehicles including automobiles, motor cycles and boats and includingoutboard marine engines.

We claim:
 1. A method of fuelling a two stroke cycle spark ignitedengine having a cylinder in which a combustible charge is prepared, anda cylinder head closing one end of said cylinder, an ignition meansmounted in said head to ignite the combustible charge, a pistonsupported to reciprocate in said cylinder, and an exhaust port in thewall of said cylinder spaced in the axial direction from said cylinderhead, said method comprising injecting a metered quantity of fuel intothe cylinder from a single injector located in the cylinder wall betweenthe level of the exhaust port and the cylinder head, said fuel beinginjected in the form of at least two individual streams, said streamsbeing arranged so a first part of the fuel is directed towards theignition means in the cylinder head and a second part of the fuel isdirected into that portion of the cylinder on the opposite side of adiametral plane of the cylinder at the location of injection of the fuelto the cylinder head.
 2. A method of fuelling an engine as claimed inclaim 1, wherein said fuel is injected in the form of three or morestreams at least one of which is directed toward the ignition means inthe cylinder head.
 3. A method of fuelling an engine as claimed in claim1 or 2, wherein the streams diverge from the injection location and arearranged to be located substantially within a cone diverging from theinjection location and having an included angle between 90° and 150°. 4.A method of fuelling an engine as claimed in claim 1 or 2, whereinbetween 30 and 70 percent of the fuel injected per combustion cycleforms said first part of the fuel.
 5. A method of fuelling an engine asclaimed in claim 1, wherein the fuel is injected in the form of threestreams, one directed into that part of the cylinder between thecylinder head and said diametral plane to form said first part of thefuel.
 6. A method of fuelling an engine as claimed in claim 5, whereinbetween 30 and 70 percent of the fuel injected per combustion cycleforms said first part of the fuel.
 7. A method of fuelling an engine asclaimed in claim 1 or 2, wherein an air inlet port is provided in thatside of the cylinder opposite the exhaust port and the location at whichthe fuel is injected to the cylinder is in that said side of thecylinder.
 8. A method of fuelling a two stroke cycle spark ignitedengine having a cylinder, a piston reciprocable in said cylinder, acylinder head closing one end of said cylinder, a cavity in saidcylinder head communicating with the cylinder and containing an ignitiondevice, an exhaust port in the cylinder spaced from said cylinder head,and an air inlet port in the cylinder in the side of the cylinderopposite the exhaust port, the method comprising admitting air to thecylinder through said air inlet port, while the air is being admittedinjecting fuel into the cylinder at a single location different from theair inlet port and in said side of the cylinder between said air inletport and the cylinder head, said fuel being injected in the form of atleast two individual streams, said streams being arranged so a firstpart of the fuel is directed towards the ignition means in the cylinderhead and a second part of the fuel is directed into that portion of thecylinder on the opposite side of a diametral plane of the cylinder atthe location of injection of the fuel to the cylinder head.
 9. A methodof fuelling an engine as claimed in claim 8, wherein the part of thefuel directed towards the cavity is 30 to 70 percent of the quantity offuel injection per combustion cycle.
 10. A method as claimed in claim 8or 9, wherein the fuel is injected in the form of three or more streams,at least one of which is directed in said direction towards the cavityin the cylinder head.
 11. A method as claimed in claim 10, wherein thefuel is injected in the form of at least three streams, two of saidstreams being directed into said part of the cylinder on said oppositeside of the said diametral plane, each of said two streams divering inopposite directions from the axial plane of the cylinder passing throughthe location of injection.
 12. A method as claimed in claim 11, whereinthe streams of fuel form a spray pattern located substantially within acone diverging from the injection location having an included anglebetween 90° and 150°.
 13. In a two stroke cycle spark ignited enginehaving a cylinder in which a combustible charge is prepared, a cylinderhead closing one end of said cylinder, an ignition means mounted in saidhead to ignite the combustible charge, a piston supported to reciprocatein said cylinder, and an exhaust port in the wall of the cylinder spacedin the axial direction from the cylinder head, the improvementcomprising a single nozzle means through which fuel is injected to thecylinder and located in the cylinder wall between the level of theexhaust port and the cylinder head, said nozzle means for directing thefuel in the form of at least two individual streams, with a first partof the fuel directed towards the ignition means in the cylinder head anda second part of the fuel directed into that portion of the cylinder onthe opposite side of a diametral plane of the cylinder at the locationof injection of the fuel to the cylinder head.
 14. The engine claimed inclaim 13, wherein the nozzle means is adapted to inject the fuel in theform of three or more streams at least one of which is directed in saiddirection toward the ignition means in the cylinder head.
 15. The engineas claimed in claim 13, wherein the nozzle means is adapted so thestreams of fuel issue as diverging streams in a form locatedsubstantially within a cone diverging from the nozzle means and havingan inclined angle between 90° and 150°.
 16. The engine as claimed inclaim 13, 14 or 15, wherein the nozzle means is adapted so that fuelissues therefrom to deliver between 30 and 70 percent of the fuelinjected per combustion cycle into that part of the cylinder between thecylinder head and a diametral plane of the cylinder passing through theinjection nozzle means.
 17. An internal combustion engine as claimed inclaim 13, 14 or 15, being an outboard marine engine.